import java.util.*;
import java.lang.*;
import java.io.*;
class Read{
    StringTokenizer st = new StringTokenizer("");
    BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
    String next() throws IOException{
        while(!st.hasMoreTokens()){
            st = new StringTokenizer(bf.readLine());
        }
        return (String)st.nextToken();
    }
    String nextLine() throws IOException{
        return bf.readLine();
    }
    int nextInt() throws IOException{
        return Integer.parseInt(next());
    }
    long nextLong() throws IOException{
        return Long.parseLong(next());
    }
    double nextDouble() throws IOException{
        return Double.parseDouble(next());
    }
}
//数字转为excel表格对应字母（27进制）
public class Main {
    public static void main(String[] args) throws IOException{
        Read read = new Read();
        Long n = read.nextLong();
        StringBuilder b = new StringBuilder();
        while (n>0){
            n--;
            long c=n%26;
            b.append((char) ('A'+c));
            n/=26;
        }
        System.out.println(b.reverse());
    }
}